Evolution of 

 Photosynthetic Mechanisms* 



Melvin Calvin f 



Department of Chemistry and 



Lawrence Radiation Laboratory 



University of California, Berkeley, California 



Introduction 



I have found the planning of today's discussion to be particularly 

 difficult, perhaps the most difficult one that I have ever undertaken. 

 The reason for this, I consoled myself, lies in the very nature of the 

 evolutionary process itself. In physical science (and particularly in 

 mathematical sciences) we are accustomed to a single sequence of 

 events, in which each idea is precursor to the next, and one gradually 

 develops a whole pattern of thought — a whole notion from beginning 

 to end — in a single sequence. Those of you who are more familiar with 

 the way biological material has evolved will know that this is not 

 really the way the living organism can be described in its evolutionary 



* The preparation of this paper was sponsored by the U.S. Atomic Energy Com- 

 mission. 



t Research Professor of Chemistry, 1960-1961. in the Miller Institute for Basic 

 Research in Science, University of California, Berkeley. 



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